Concrete Blocks

Membership and Properties

The process of industrially producing blocks in a block plant goes through several stages as follows:

First Stage:

This phase includes the collection of ingredients to be mixed in an appropriate proportion in conformity with the set specifications. Then, such ingredients are put inside a mixer.

The Mixer:

It is used to mix the ingredients used for block-making. Then the mix is placed on a metal basin with a diameter of 1.5 meters; this basin is also called " basket." (Each basket produces 15 batches). Then the mixer is operated by an electric motor. As electricity is supplied, the mixer's shafts which are inside the basin would rotate to mix the ingredients and homogenized them.

Components Composing Blocks - the mix.

  • Portland Cement 2. sesame gravels which are classified based on the rocks of extraction:
    Syaline Rocks, revavine rocks and basalt rocks.
  • Gravels used in block making are called the mountain gravel, for it has two hues, one is dark brown and the other is light brown.
  • Note: If there are any clay veins in the gravel, the gravel must be properly washed and freed of such impurities.

  • Sand: Clean sieved sand of SW type
  • water: a clean drinkable
    • Ingredients: 2 Cement bag + 1.4 ton of gravel + 200 kg of sand + 30 - 70 kilos of water
    • Water quantity varies according to the seasons; in summer, amount of water = 70 kg; in winter= 30 kg
  • Note: These amounts should be enough to fill the basin/ basket in order to produce 60 bricks, each weighing 1.6 kg.

  • Manufacturing Process:
    This starts by running the mixer.

    • We should put the following amounts in the mixer: 200 kg of sand + 600 kg of gravel + 100 kg Cement + additional 800 kg of gravel; then water is poured into the mixer.
    • We must wait for 15 minutes from the beginning of the operation to its ending. A homogeneous mixture should the outcome. 30% of the mix should be dry.

    Second Stage:
    At this stage, the mixture must be transmitted from the mixer to the molding machine. The mixture should be conveyed by using tricyle carriers ( to be pushed manually).
    Each tricycle should be filled with the mix and head to the machine. Then the mix is poured into the machine which starts to compress the bricks into the desired shape inside metal molds.
    These molds are accurately manufactured in accordance with the required sizes. It is also necessary to use the mechanical shaking method to make sure that the mix is compacted to the most possible degrees.

    Third Stage:

    • After taking them out of their molds, the bricks are dried for 3 hours.
    • Heavy water spraying of bricks must be done 3 times a day and should continue for 48 hours.
    • After drying, the bricks are moved in the form of rows on the ground to wooden molds which are then wrapped and shipped.

    Note: Wooden molds differ in the number of bricks to incorporate, depending on their types: A mold may take

    • 75 blocks …… 20 cm each.
    • 80 blocks ……… 17 cm each.
    • 85 blocks …… 15 cm each.
    • 125 blocks ……… 10 cm each.

    Note:
    The higher the ratio of water is during mixing, the heavier the brick is.
    Blocks should be used in masonry work or construction only after 7 days from their production.
    Blocks should be water-sprayed only once when they are on molds.

Types of Blocks

Cement-Made Bricks: It is most used type in Gaza and is made of cement, sand and sesame gravel. The weight of this type of bricks could be increased if one uses normal aggregates. The weight could be reduced to half if light aggregate (pumice stone) is used.

There are three types of cement made bricks:

  • Solid Block: This type has no holes, except two rounded openings with a 10 cm diameter each. In the past this type was used to build load-bearing walls, for its flexure resistance is not less than 70 kg / cm³, Its sizes are as follows: 40 × 20 × 20 cm and 40 × 20 × 15 cm.
  • Normal Hollow Blocks: Hollow blocks are divided into several types in accordance with their sizes as illustrated by the table below:
    • L 40 40 40 40 40 40
    • W 20 20 20 20 20 20
    • T 4 7 12 10 15 20

Cement Brick Testing
Brick physical testing is performed to determine that bricks:

  • are free of clay and coal and have one color.
  • have relatively smooth touch; it is preferred to be coarse so that plaster holds easily to their surfaces. In case of bricks that do not need any plastering, it is preferred to produce them with smooth and soft surfaces.
  • have regular and similar sizes and dimensions as stipulated in the specification. It is also important to ensure that the internal facets of blocks are lined with the sides of compression.
  • have no cracks, fractures, defects of any form that may affect the block strength.

Laboratory testing is performed to examine: examination and laboratory lies in:

  • Block durability (resistance to flexure). This should not be less than about 35 Kg / cm².
  • Block weight in isolation; its weight should not be more than the default weight.

Preparations for Using Blocks in Masonry or construction :

  • All broken blocks should be removed from the work site.
  • the construction site must be cleaned by sweeping it and all concrete masses should be removed by using a hammer. Then, the place should sprayed with water.
  • Lay a strong string and stretch from the corner of the top floor to the corner of the bottom floor.

Tools used in the Building of Blocks:

  • Carrier: It is used to carry mortar from the basin.
  • Leveling Device: IT is used to level the wall horizontally and vertically
  • Mason String: it is used to keep the wall on one leveling.
  • Basin: it is used to keep the mortar inside
  • Plumb Line: It is used to ensure that the wall is vertically straight.
  • Linear tape or meter: it is used to determine the required lengths and dimensions.
  • chisel and hammer: they are used to cut the blocks into the dimensions.

Mortar Definition:

It is paste used to bind building blocks or units in order to build the required wall. The mortar used in masonry work is composed of :

  • Cement: It is the main component for a reaction to take place.
  • Sand: It is a substance used for filling and has no role in the reaction taken place in a mix. Sieved sand should be used. It is also used to reduce any changes to a mortar's volume.
  • Water: It trigger the reaction taken place in a mix. It should be clean and drinkable. There should be neither organic substances nor clay in the used water. The sand should be free these impurities as well.

Mortar Quantities :

to be used (based on volume): 1 cement bag: 3 sand; water ratio should be (0.6-0.7) of the total amount of cement.